Perivascular wall tumors (PWTs) are defined as neoplasms deriving from mural cells of blood vessels, excluding the endothelial lining. The spectrum of human cutaneous PWT includes glomus tumor, hemangiopericytoma (HEP), myopericytoma, angioleiomyoma/sarcoma, angiomyofibroblastoma, and angiofibroma. The purpose of this study was to revise clinical presentation, cytology, histopathology, and immunohistology of canine cutaneous PWT with cytology typical of canine HEP. Diagnosis was established on the basis of vascular growth patterns (staghorn, placentoid, perivascular whorling, bundles from media) and immunohistology, including 7 smooth muscle markers and the cell membrane ganglioside of unknown origin recognized by the antibody 3G5 (CMG-3G5). Twenty cases were included. Ages ranged from 6 to 13 years; 12 dogs were males and 8 were females, and there was a prevalence of crossbreeds. Tumors arose from a single site with preferential acral location (10/20). Cytology revealed moderate to high cellularity in all cases, cohesive groups of cells (19/20), capillaries (18/20), and bi- to multinucleated cells (18/20). Six myopericytomas, 5 angioleiomyomas, 2 angioleiomyosarcomas, 2 HEP, 1 angiofibroma, and 1 adventitial tumor were identified. A definitive diagnosis was not possible in 3 cases. Smoothelin, heavy caldesmon, desmin, myosin, calponin, and CMG-3G5 were the most valuable markers to differentially diagnose canine PWT. Similar to reports in humans, canine HEP embodied a spectrum of neoplastic entities arising from different vascular mural cells. Before canine PWTs are assimilated into one prognostic category, a consistent classification and characterization of their biology is necessary. As proposed in humans, HEP should also be considered a diagnosis of exclusion in dogs.

Clinicopathologic and immunophenotypic characteristics of large granular lymphocyte (LGL) neoplasia in 21 cats were examined. All cats were domestic short (19) or long hair (2) with a mean age of 9.3 years at diagnosis. Increased peripheral blood LGL counts were present in 18/21 cats. Neutrophilia (12/21 cats) and increased serum liver enzymes (7/12), total and direct bilirubin (7/13), BUN (5/14), and creatinine (2/14) were observed. Cats usually presented with advanced disease and none survived longer than 84 days (mean 18.8 days) postdiagnosis. Cytologically, LGLs had a mature (6/21), immature (13/21), or mixed (2/21) morphology. Necropsy lesions consisted of neoplastic lymphoid infiltrates in the jejunum, ileum, and duodenum in decreasing order of frequency. In the small intestine, mucosal ulceration (9/13) and epitheliotropism of neoplastic cells (9/13) were common. Neoplastic infiltrates were also present in the mesenteric lymph nodes (13/13), liver (12/13), spleen (8/13), kidneys (5/7), and bone marrow (5/7). A T cell phenotype (CD3epsilon+) characterized LGL neoplasia in 19/21 cases. A CD8alphaalpha+ cytotoxic/suppressor phenotype was present in 12/19 T cell tumors, 2 had a CD4+CD8alphaalpha phenotype, 3 had a CD4-CD8- phenotype, and 2 were CD4+ helper T cells. CD8beta chain expression was not detected in any instance. In two cats, a B or T cell origin could not be established. CD103 was expressed by 11 of 19 (58%) of the lymphomas tested. The immunophenotypic features shared by neoplastic LGLs in the cat and feline intestinal intraepithelial lymphocytes (IELs) support a small intestinal IEL origin for feline LGL lymphoma.

Background: In the clinical staging of cutaneous mast cell tumors (cMCT), the diagnosis of metastasis is controversial based on cytological examination of lymph nodes, spleen, liver, bone marrow, and blood.Objectives: To define the prognostic role of ultrasound-guided cytology of spleen and liver in cMCT. The results of cytological evaluation were compared in relation with survival time.Animals: Fifty-two client-owned dogs with a diagnosis of cMCT. Methods: Selection of cases was based on cytological evaluation of liver and spleen to detect infiltration at distant sites. The Kaplan Meier method was used to compare survival in dogs with and without infiltration of spleen and liver (log-rank test P o .05).Results: Ten dogs with cMCT had mast cell infiltration of spleen, liver, or both and 4 of these dogs had involvement of the regional lymph nodes. The majority of dogs had 2 or more ultrasonographically abnormal findings simultaneously in spleen and liver. Nine dogs had grade II cMCT, and 1 had grade III cMCT. Dogs with positive evidence of mast cell infiltration to spleen, liver, or both had shorter survival times (34 versus 733 days) compared with dogs negative for mast cell infiltration at distant sites.Conclusion and Clinical Importance: Dogs with evidence of mast cell infiltration at distant sites have a shorter survival times than dogs without evidence of infiltration at distant sites. This study suggests that cytology of spleen and liver is indicated either for ultrasonographically normal or for ultrasonographically abnormal spleen and liver in dogs with cMCT.

Absence of the aforementioned combination of variables at diagnosis may help identify dogs with lymphoma that will not survive > 2 years. Other types of neoplasia, in particular osteosarcoma, may develop in long-term-surviving dogs.

The cytologic characteristics of canine AS are widely heterogeneous, but supplementary findings can provide clues that are useful for making a cytologic diagnosis. Histologic and immunohistochemical confirmation is nonetheless warranted in all cases.